Reciprocating apparatus in the form of positive displacement compressors or engines in which pistons move in cylinders are all worked in conditions of high friction between moving adjoined surfaces that require lubrication that is usually applied in environments of considerable heat. When used for the movement or compression of some gases, the oxidation of the lubrication is objectionable and contributes to the friction condition and the normal heat escalation of compression. This friction adds to the requirement for cooling the gas product that is compressed and to also increases the the cooling requirement of the engine or compressor block itself.
In an opposite sense the fan-like turbine structures that employ blades and impellers moving in close proximity to a surrounding stator have no friction factor but are not positive in displacement and are operated at extremely high speeds to overcome the slip-bypass in the space between blade tips and the stator vanes. This often involves the addition to the turbine shaft of an elaborate and precision gear train reduction system to bring speeds down to usable operational levels.
In many of the gas pumping and refinery situations, line drive dependence is upon combustion engines as the prime movers for the pumping apparatus used. These waste as much as 75% of the energy input in expended heat energy that goes up the exhaust stack. Electrical prime movers are more efficient, but there is always a potential for a spark-generated explosion and, in the refinery atmospheres, corrosion problems as well as explosion proofing make these electrical drives high in capital cost and costly to maintain.
In each existing instance, there is a great heat loss in the compressor itself as well as the heat loss in the driving engines or motors, so efficiency is frequently as low as 40 percent. Much of the heat generated in compression is transferred to the gases being compressed, leading to substantial work and cost involved in ancillary cooling equipment required to bring down the temperature of the compressed product gas. An example is Natural Gas that, when recompressed for delivery in a pipeline, must be cooled to about 100 degrees F. before it can be put back in the line and the gas used in refinery processes that require compression, where heat input is critical, also require elaborate cooling means before return to the process.
The equipment associated with this invention involves less in capital investment because it is smaller and more simple in design and therefore it is more easy to maintain.
In refinery practice there is a requirement for the high pressure compression of hydrogen. When this is done with conventional compression techniques each of several compression steps must be followed by high output cooling apparatus that has a significant energy input and is again highly capital intensive.